* {
  margin: 0;
  padding: 0;
  list-style: none;
  box-sizing: border-box;
}

html,
body,
#root,
.App {
  width: 100%;
  height: 100%;
}

.App {
  display: flex;
  flex-direction: column;
}

.header {
  width: 100%;
  height: 50px;
  display: flex;
  align-items: center;
  background: #f90;
  justify-content: space-around;

}

.on {
  background: pink;
}